For years, height has been labeled a genetic trait, although scientists have been unable to pinpoint which specific genes are responsible for the trait. In a recent mass genetic study, researchers have discovered the "missing heritability" genes of people of European descent.
The paper was recently presented at this year's the American Society of Human Genetics meeting by international researchers. The study included 4.1 million where the geneticists identified about 10,000 DNA markers associated with height across five major ancestries. Common single nucleotide polymorphism (SNPs), or regions in the genome where genetic variations are found, was identified in up to half of the people with European ancestry.
Loïc Yengo from the University of Queensland said that if the missing heritability genes can be extended across other ancestries, there would "contribute to personalized medicine." For instance, genome scans would give more accurate assessments of an individual's risk of a specific disease.
Searching for Missing Heritability
Searching for the height genes began in the early 2000s as described in the 2008 study "Personal genomes: The case of the missing heritability." At the time, three sets of genome-wide association studies uncovered over 40 genes associated with height variation.
Missing heritability has also been associated with identical and fraternal twins. There are also missing genes that researchers continue to search for that are factors of autism, schizophrenia, obesity, diabetes, and heart disease.
There are many factors associated with height, explained the researchers, such as social status, diet, and childhood illnesses. Despite the significant find of identifying height-related genes, the DNA markers only affected 5% of height variation.
Height-related genes are quite complex. For example, two people share the same SNP variation in a common location, they may also have the same version of a height-related gene. However, one person could have another rare genetic mutation that results in not having the same height as the person with the same height gene.
Variant and Mutated Genes
Professor Leonid Kruglyak from Princeton University said that every gene could have a variant associated with height. "You're talking about thousands of variants that you would have to invoke to get near 80% or 90% heritability."
In another study that looked for trait heritability, researchers conducted a whole-genome sequence of people who carried rare genetic variants. About 50% of variants were associated with inherited height and body mass index.
There are still many missing heritability genes, concluded the geneticists, but more data could be gathered when more people have complete DNA scans. In the meantime, some scientists remain unsatisfied that they've only identified biomarkers linked to genes that affect height, but not specific genes.
Nevertheless, the study gives a better understanding of how to find genes that influence height. Instead of studying the entire genome of each individual, researchers can only focus on about one-third of the genome and biomarkers for height.
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